New Zealand First leader Winston Peters is being challenged to prove his party’s claims surrounding the grounding of an Interislander ferry amid refusals to front to some media.

Labour leader Chris Hipkins says NZ First’s claim the Aratere’s grounding last month was because of the vessel’s autopilot being left on too long during a coffee run is a “serious allegation” and indicates Peters is not holding himself to his own standards.

“Winston Peters is the first to lambast anyone who makes an allegation that might in any way negatively reflect on him and demand that they front up immediately with the proof,” Hipkins told the Herald.

“New Zealand First has made a pretty big allegation here and they should front up with their evidence.”

The claim was posted to NZ First’s X account yesterday.

“Is it true that the Aratere ran aground when someone put the autopilot on, went for a coffee, and then couldn’t turn the autopilot off in time when that someone came back ... ?”, it read.

KiwiRail, which owned and operated the ferries, had contested this by confirming the requirement to have a “regulated number of qualified people” on the ship’s bridge at all times was met on the night of the grounding.

It did not address matters concerning the use of an autopilot function: “As formal investigations are ongoing, we will not be making further comment,” Interislander executive general manager Duncan Roy said.

Maritime NZ branded the speculation “unhelpful”, given the grounding was being investigated. Maritime Union of New Zealand national secretary Carl Findlay said it was “terrible” and empathised with ferry workers who would now be in the spotlight following the claim.

Maritime lawyer Troy Stade, engaged by the union, said he could “categorically” rule out the involvement of any beverages.

Asked whether a problem with the autopilot system was related to the grounding, Slade said they were investigating all avenues.

“It’s public knowledge that the steering system was refitted earlier this year by KiwiRail. We are looking into the extent to which that system played a part, as part of an ongoing investigation.”

As to whether there was any indication of human error with using that new steering system, Slade said he was not aware of that being a factor.

Neither Marlborough harbourmaster Jake Oliver nor Transport Minister Simeon Brown commented on NZ First’s claim.

Peters has refused to comment to several media, including the Herald, about what evidence his party had to support the allegation and whether it had informed investigators.

Peters, who is currently the acting Prime Minister with Christopher Luxon in the United States, did appear on The Country radio show today and said he’d be looking into the matter after reading the response from KiwiRail in the Herald.

He argued the social media post was not his but that of his party. Challenged on this, Peters maintained he didn’t have enough time to be across all party matters.

Labour leader Chris Hipkins is calling on NZ First and Peters to front up and provide proof. Photo / Mark Mitchell

Hipkins accepted party leaders might not know everything their party posted online but he expected Peters would have been aware.

“Winston Peters is New Zealand First and New Zealand First is Winston Peters.

“It’s a big allegation to make without running it past the leader.”

Hipkins said it was “extraordinary” for such a claim to come from a party led by someone acting as the country’s Prime Minister.

“If they’ve got proof and evidence of it, then they should be sharing that with a degree of urgency.

“If they haven’t, then they shouldn’t have made the claim.”

The Aratere left Picton at 9.45pm on June 21 before suffering a reported steering failure and running aground shortly after. It is berthed at Waimahara Wharf in Picton and remains under a detention order. The ship cannot leave until Maritime NZ says it is safe.

Adam Pearse is a political reporter in the NZ Herald Press Gallery team, based at Parliament. He has worked for NZME since 2018, covering sport and health for the Northern Advocate in Whangārei before moving to the NZ Herald in Auckland, covering Covid-19 and crime.